1. Field of the Invention
The present invention relates to a device for suspending and guiding a movable panel or a similar load, especially for an oblique-displacement sliding door of the type employed in railroad cars. This invention is also directed to an oblique-displacement sliding door equipped with a device of this type.
2. Description of the Prior Art
The disadvantage of sliding doors lies in the fact that, in order to provide a tight seal at the time of closing, each door-edge face must come into contact with a surface which is perpendicular to the plane of closure. The external surfaces of the volume to be closed are therefore displaced to an extent corresponding to the thickness of the door. While this drawback is negligible in the case of interior doors such as cupboard doors, it becomes objectionable in the case of vehicles having doors of greater thickness which are required to provide an effective fluid-tight seal. Furthermore, variations in the external surface of the vehicle must be reduced to a minimum.
A known type of door accordingly undergoes a rectilinear longitudinal movement of translation during the main displacement of the door either for providing free access or for closing the opening and then, at the end of the closing movement of travel, undergoes an oblique movement of translation such that the door comes into position in the line of extension of the external surface of the volume to be closed. Doors of this type are designated as "oblique-displacement sliding doors". Once the door is closed, the external surface of the closed volume such as a vehicle has satisfactory continuity.
In the following description, the meaning of the term "translation" will be retained in its mathematical sense, in which a segment which joins two points of the panel remains parallel to itself and the vector representing the displacement of the panel has a direction either parallel to the plane of this latter or oriented transversely with respect to said plane.
Known devices which permit this double movement of longitudinal rectilinear translation followed by a transverse movement of translation are usually composed of rolling elements which run on one or a number of straight rails secured to the movable load by means of one or a number of bayonet-type double-elbowed shafts which undergo a movement of pivotal displacement at the end of the closing path of travel so that the door accordingly undergoes a curved movement of translation. The shaft or shafts pivot through an angle such that the door comes into position in the line of extension of the external surface of the volume to be protected.
Devices of this type must necessarily be provided with springs in order to ensure that the double-elbowed shafts open the door to the maximum extent during the rectilinear movement of translation and that this movement takes place in a predetermined and non-random manner. These springs must have a certain degree of stiffness, with the result that the user has to exert a greater effort in order to overcome the pressure of these springs during the final stage of closing in a curved movement of translation. While devices of this type may prove suitable in the event that the door is actuated by a jack, this is hardly the case if the door is actuated by an operator who has only moderate or low strength. In the case of heavier doors such as those of public transportation vehicles, the assistance of a jack is essential.
Suspension and guiding devices comprising conventional rolling elements such as rollers or wheels in cooperating relation with one or a number of rails which are partly rectilinear and partly curved are suitable for complex and costly uses such as industrial handling operations but cannot be contemplated for a vehicle door on account of their complexity and high cost. Furthermore, these devices require periodic maintenance and lubrication which impose additional demands on the user.
Another known type of suspension and guiding device comprises two rollers mounted on a common shaft and adapted to cooperate with two opposite rolling surfaces, with the result that the rollers rotate in opposite directions with respect to each other, these devices being primarily intended to support and guide French windows, sliding screens or anti-insect netting frames which are so arranged as to permit easy installation and removal. While devices of this type permit good suspension at the time of rectilinear translational motion, they offer only a very limited possibility of guiding which provides only for lateral reactions in one direction. These devices do not permit the construction of an oblique-displacement sliding door for vehicles.
For example, a guiding device is known in which a single roller runs on one side on a flange and a cylindrical roller runs on a flat surface, these two rollers being mounted on the same shaft which is attached to the load. This known device is intended to permit very rapid demounting of the door. Furthermore, a horizontal tractive force exerted at the level of the rolling element makes it possible to move the cylindrical roller away from the flat surface by sliding the single roller along the flange. This clearly shows that a device of this type is not suited for a vehicle door and that the guiding device could not follow sharp curves which would be liable to cause detachment of the cylindrical roller from the flat surface.
Furthermore, no provision has been made for any oblique displacement. Finally, an upward thrust exerted on the panel, as occurs at the time of a jolt of the vehicle, has the effect of detaching the assembly formed by the two rollers hereinabove described, thus disengaging the rolling element from the guide track, which is not suitable in the case of a vehicle door.